Audi A4/S4/RS4 B9 Reliability Guide (U.S. Market and Global Overview)
The Audi A4, S4, and RS4 B9 generation, launched in 2016, continued Audi’s evolution toward more technology, efficiency, and luxury. Built on the MLB Evo platform, this generation brought lighter weight, new engines, and advanced driver-assistance systems.
While the B9 feels more refined and high-tech than ever, long-term ownership has revealed a few reliability concerns—mostly around electronics, sensors, and maintenance-sensitive engines. This guide will help you understand what to expect from each version, what problems to watch for, and how to keep your B9 performing at its best.
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Overview: How Reliable Is the Audi A4/S4/RS4 B9?
The B9 generation earns praise for build quality and comfort, but its reliability is average rather than exceptional.
The good news: major mechanical failures are rare compared to older generations.
The bad news: electronic glitches, minor oil leaks, and turbo-related wear are common after several years.
Overall, the B9 performs well when properly maintained, especially with timely oil changes and software updates. For buyers, the key is finding a car with a full service history and updated software (many reliability issues have been fixed via dealer updates).
Common Problems Across the Audi B9 Platform
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Infotainment and digital cluster bugs: MMI freezes, unresponsive touchscreens, or occasional software crashes.
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Oil consumption: Still present on some 2.0 TFSI engines, though less severe than in the B8.
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Coolant leaks: From plastic water pumps and thermostat housings, particularly on early builds.
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Carbon build-up: Direct-injection engines can develop carbon deposits over time, leading to misfires or rough idle.
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Electrical sensor faults: Check-engine lights caused by faulty oxygen, boost, or knock sensors.
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DSG/S-Tronic issues: Some early B9 S4s reported harsh shifts or mechatronic control unit problems.
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Turbo wastegate rattle: Common minor annoyance on 2.0 TFSI engines as mileage increases.
Engine-by-Engine Reliability Breakdown
2.0 TFSI (A4 B9)
The most popular engine in the B9 A4, this turbocharged four-cylinder is smoother and more efficient than its predecessor.
Known problems:
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Oil consumption (improved but not eliminated compared to B8).
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Carbon build-up on intake valves (common on direct-injection engines).
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Wastegate rattle or turbo actuator issues.
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Water pump and thermostat leaks from plastic housings.
Maintenance tips:
Perform oil changes every 5,000 miles using VW 508.00-approved oil, inspect for coolant leaks, and consider walnut blasting every 60,000 miles. Regular maintenance prevents most major issues.
3.0 TFSI V6 Turbo (S4 B9)
In the S4 B9, Audi replaced the previous supercharged engine with a single twin-scroll turbocharged V6. It delivers strong performance and improved efficiency, but also introduces new potential trouble spots.
Known problems:
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PCV valve failures causing rough idle or vacuum leaks.
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Water pump leaks (less frequent but still possible).
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Occasional carbon build-up over time.
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DSG/S-Tronic transmission judder or delayed engagement in early models.
Maintenance tips:
Use premium fuel only, keep up with DSG fluid service every 40,000 miles, and ensure all software updates have been applied. This engine can easily last over 200,000 km with proper maintenance.
2.9 V6 Biturbo (RS4 B9)
The RS4 B9’s 2.9-liter twin-turbo V6, shared with the RS5, offers incredible performance but demands meticulous upkeep.
Known problems:
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Turbocharger oil line leaks or failures if oil change intervals are stretched.
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High intake temperatures can lead to carbon deposits on intake valves.
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Cooling system complexity (two turbos mean more hoses and potential weak points).
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Expensive maintenance due to tightly packaged engine bay.
Maintenance tips:
Change oil every 5,000 miles, use high-quality synthetic oil, and monitor turbo performance closely. Avoid cars that have been tuned without upgraded cooling or frequent oil changes. When maintained, this engine is robust and capable of high mileage.
Other Reliability Considerations
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Brakes and suspension: Heavy cars with powerful engines—expect more frequent wear of pads, rotors, and control arms.
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Electronics: Lane assist, adaptive cruise, and parking sensors can malfunction due to software or sensor calibration issues.
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MMI and virtual cockpit: Occasional glitches, mostly fixed by software updates.
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Interior trim and screens: Some early B9s show wear on soft-touch materials or screen delamination after years of heat exposure.
Verdict: Is the Audi A4/S4/RS4 B9 Reliable?
The Audi B9 platform is more dependable than the B8 overall—but still not maintenance-free.
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The 2.0 TFSI is efficient and durable when serviced properly.
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The 3.0 TFSI offers excellent performance and remains relatively reliable.
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The 2.9 Biturbo in the RS4 delivers thrilling power but demands expert care and short service intervals.
Overall, the B9 series offers a strong balance between luxury and performance, with reliability largely determined by how well the car has been maintained. Choose a one-owner example with full dealer service records, and you’ll likely enjoy years of trouble-free driving.
What to Check Before Buying a Used Audi A4/S4/RS4 B9
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Verify complete service history—especially oil and coolant system maintenance.
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Confirm all recall campaigns and software updates have been done.
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Inspect for coolant leaks around the thermostat or water pump.
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Listen for turbo rattle or hesitation under boost.
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Test infotainment responsiveness and all driver-assist functions.
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On DSG/S-Tronic cars, check for smooth shifting and prompt engagement.
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Avoid heavily tuned or modified cars unless professionally maintained.
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